The effect of anatase TiO2 surface structure on the behavior of ethanol adsorption and its initial dissociation step: A DFT study

Abstract

The perfect and defective surfaces of anatase TiO2 including (101) and (001) surfaces have been chosen to probe into the effect of anatase TiO2 surface structure on the behavior of ethanol adsorption and initial dissociation step. Here, the results are obtained by density functional theory (DFT) calculation together with the periodic slab model. Our results show that the surface structure of anatase TiO2 can obviously affect the behavior of ethanol adsorption and the catalytic activity of its initial dissociation step; firstly, on the perfect and defective surfaces of anatase (101), ethanol dominantly exists in the form of molecule adsorption; however, ethanol is the dissociative adsorption on the hydroxylated anatase (001), and the coexistences of molecular and dissociation adsorption modes on the perfect anatase (001). On the other hand, the initial dissociation step of ethanol with molecule adsorption prefers to begin with its O–H bond cleavage leading to CH3CH2O and H species rather than the cleavage of its α-C–H, β-C–H, C–C and C–O bonds, namely, the preferable O–H bond cleavage for the initial dissociation step of ethanol is independent of the surface structure of anatase TiO2; however, the corresponding catalytic activity of ethanol initial dissociation step with the O–H bond cleavage on different anatase TiO2 surfaces is in the following order: hydroxylated (001)>perfect (001)>defective (101)>perfect (101), suggesting that the catalytic activity for the initial dissociation step of ethanol is sensitive to the surface structure of anatase TiO2, and the hydroxylated (001) is the most favorable surface. Among these surfaces, the most favorable product for the initial dissociation step of ethanol is CH3CH2O species.